align behaviour of __replace__

eendebakpt · Sep 16, 2023 · Sep 16, 2023 · Sep 16, 2023 · Sep 16, 2023 · Sep 25, 2023
commit c97105f0012f7e8380e469e81f25b56322bf50b4
diff --git a/Lib/copy.py b/Lib/copy.py
@@ -301,7 +301,7 @@ def replace(obj, /, **changes):
     frozen dataclasses.
     """
     cls = obj.__class__
-    func = getattr(cls, '__replace__', None)
-    if func is None:
+    func = getattr(cls, '__replace__', _NoValue)
+    if func is _NoValue:
         raise TypeError(f"replace() does not support {cls.__name__} objects")
     return func(obj, **changes)
diff --git a/Lib/test/test_copy.py b/Lib/test/test_copy.py
@@ -981,6 +981,13 @@ class C:
         with self.assertRaisesRegex(TypeError, 'unexpected keyword argument'):
             copy.replace(c, x=1, error=2)
 
+    def test_invalid_replace_method(self):
+        class A:
+            __replace__ = None
+        a = A()
+        with self.assertRaises(TypeError):
+            copy.replace(a)
+
 
 def global_foo(x, y): return x+y